At present, the common hydraulic horizontal jacks in the market mainly include a frame, a hydraulic unit, a jib unit, a link rod, and a handle, wherein, the jib unit includes a jib and a bracket arranged on the jib; one end of the link rod is pivotally attached to the frame, and the other end of the link rod is hinged to the bracket of the jib unit. When a heavy object is to be lifted, the handle can be pressed repeatedly, so that the hydraulic unit will drive the jib unit to lift upwards, and finally the bracket of the jib jacks up the heavy object. A drawback of the structure described above is: for the hydraulic horizontal lifting jacks with the same standards (i.e., the parameters such as oil pressure and stroke, etc. are constant), the lifting height and bearing capacity are constant because the lengths of jib and link rod can not be adjusted. Therefore, it has limited function and is applied only in a narrow field. To overcome the above drawbacks, a type of hydraulic horizontal jack with a high tray is introduced into the market. However, such a hydraulic horizontal jack improves nothing except increasing the height of the lowest position, and still has limited function.